The invention relates to a contact adhesive and adhesive system for EPDM elastomers. More particularly, the invention relates to an adhesive composition for bonding an EPDM elastomer to itself or for bonding an EPDM elastomer to another elastomer or to a non-elastomeric material.
EPDM elastomers have long been of interest for possible use as a roofing material, particularly for the industrial and commercial flat roofing markets. EPDM elastomers are of interest as roofing materials due to the fact that such elastomers provide significant advantages in flexibility and long term weathering resistance over conventional built up roofing (BUR) materials which are composed of tar paper composites which have poor flexibility and only very limited weathering resistance.
However, despite these advantages, the use of EPDM elastomers in roofing applications in the past has been hampered by certain disadvantages relating to the nature of the field prepared lap splice. This is a significant disadvantage since in applying EPDM sheets to a roof, it is usually necessary to splice two (2) or more EPDM elastomer sheets together. This splice or seam area is subjected to both short term and long term stresses such as those caused by roof movement, heavy winds, freeze-thaw cycling and thermal cycling. Such stresses may manifest themselves in shear forces or peel forces, i.e., the seam peels back producing an open seam under severe conditions or a partially open seam (often referred to as a fish-mouth condition) under less severe conditions.
A further disadvantage to the use of EPDM elastomers as a roofing membrane material is the lack of adhesion of EPDM to other elastomeric materials and to non-elastomeric materials which are frequently encountered on roofs, especially the flat roofs of commercial and industrial buildings. Thus, on most flat roofs of that type, there are usually metal pipes, metal vents, air-conditioning units and the like which either extend from or are attached to the roof surface. In such cases, it is necessary to apply an elastomeric flashing compound around those areas where the metal pipes, vents, air-conditioning units, etc. meet the roof surface in order to prevent water from seeping through the roof. Such elastomeric flashing compounds are conventionally composed of a neoprene type elastomer. As will be evident, it is necessary to bond the EPDM elastomer roofing membrane to the elastomeric flashing compound. In addition, it is often necesary to bond the EPDM elastomer roofing membrane to non-elastomeric materials such as wood, masonry, metal, glass, bituminous materials, insulation materials and the like.
As will be apparent from the foregoing, it is necessary to utilize an adhesive to bond EPDM elastomer roofing membranes together or to other elastomeric materials or to non-elastomeric materials. However, such an adhesive must meet a number of requirements which have proven to be extremely difficult to completely satisfy. Thus, the adhesive must provide sufficient peel and adhesive strength to permit splices formed by bonding EPDM elastomer sheets together to resist both the short term and long term disbonding forces or stresses referred to above. Moreover, the adhesive must be resistant to oxidation, hydrolysis, and chemical attack from ponded water. Furthermore, the adhesive must be capable of being used over a broad range of ambient temperature application conditions; it must have a broad range of appplication drying times; it must be resistant to attacks by ozone, nitrous oxides, sulfur dioxide and other air pollutants; it must not cause excessive swelling of the EPDM elastomer sheets in order to prevent opening of the splices; it should have a high flash point and should not be toxic to roofing installers. The adhesive should also be compatible with other elastomers and with non-elastomeric materials as well. Finally, the adhesive must provide the important property often referred to in the adhesive art as "Quick Stick." The term "Quick Stick" as used herein means the ability of two sheets of material which have been coated with an adhesive composition to develop virtually immediate adhesive strength when placed in contact with each other.
Until recently, the use of EPDM elastomers as roofing materials was hampered by the unavailability of commercial adhesives which would meet substantially all of the above requirements. However, several recent developments have resulted in the rapidly growing use and acceptance of EPDM elastomers as roofing materials. One such development has been the increasing demands by building owners and roofing installers for roofing materials having longer service life. Another development has been the increased availability of adhesives which meet many, if not all, of the above requirements.
However, along with the increased use and acceptance of EPDM elastomers for roofing materials has come additional demands for colored or pigmented EPDM elastomers such as white EPDM elastomers for use as decorative roofing materials and for reducing thermal absorption. Applicants have found that adhesive compositions which are suitable for use with conventional black EPDM elastomer roofing membranes are in some instances not suitable for other colored EPDM elastomer roofing membranes. Moreover, adhesive compositions for colored EPDM elastomer roofing membranes must meet additional requirements over and above those described above. Thus, such adhesive compositions should not cause discoloration of the colored EPDM elastomer membrane and should not bleed through the membrane. Furthermore, the adhesive should be resistant to discoloration caused by exposure to ultraviolet rays.
The prior art relating to adhesives which are specifically designed for EPDM elastomers is somewhat limited. However, adhesive compositions containing neutralized, partially neutralized or unneutralized sulfonated elastomers, tackifying resins and organic solvents or organic solvent mixtures are known in the art as shown by U.S. Pat. Nos. 3,801,531; 3,867,247 and 4,450,252.
U.S. Pat. No. 3,801,531 relates to pressure sensitive adhesive compositions which contain thiouronium derivatives of unsaturated elastomers or neutralized, partially neutralized or unneutralized sulfonated elastomers including sulfonated EPDM, tackifying resins including phenol formaldehyde or alkylphenol formaldehyde resins and organic solvents or organic solvent mixtures including a preferred 90:10 mixture of toluene and isopropyl alcohol.
U.S. Pat. No. 3,867,247 relates to adhesive contact cements which contain neutralized, partially neutralized or unneutralized sulfonated butyl elastomers, tackifying resins including phenol formaldehyde or alkylphenol formaldehyde resins and organic solvents or organic solvent mixtures including a preferred 90:10 mixture of toluene and isopropyl alcohol.
U.S. Pat. No. 4,450,252 relates to an adhesive composition which comprises a neutralized sulfonated EPDM elastomeric terpolymer having from about 10 to about 100 milliequivalents of neutralized sulfonate groups per 100 grams of terpolymer, an organic hydrocarbon solvent or mixture of organic hydrocarbon solvent and aliphatic alcohol, a para-alkylated phenol formaldehyde tackifying resin and an alkylphenol or ethoxylated alkylphenol.